The role of US in obstetrics US importance during 1st , 2nd and third trimester

1. The Role of
Ultrasound in
Obstetrics
Dr. Khalid Osman

2. Uses of 1st trimester U/S

3. 1st trimester U/S
 Confirm pregnancy , viability and
the accurate gestational age (+/-
7 days)
Gestational sac
Crown rump length

4. 1st trimester U/S
Locate the pregnancy
(intra-uterine or ectopic)
Usually by vaginal
ultrasound in early
pregnancy(>7wks)

5. 1st trimester U/S
 Diagnosis of twins and zygosity

6. 1st trimester U/S
 Diagnosis of molar pregnancy ( snow
storm appearance)

7. 1st trimester U/S
 Assessment of other pelvic masses
 e.g. fibroids, functional ovarian cysts
& neoplasms
 Screening for congenital abnormalities
 Nuchal fold measure, anencephaly
etc.
 Assisting CVS and amniocentesis

8. Uses of ultrasound in
2nd trimester

9. ultrasound in 2nd trimester
 Second trimester dating (+/- 10 days)
 Biparietal diameter, head &
abdominal circumference, femur
length

10. 2nd trimester u/s
 Assessment of APH
 Screening for placenta previa

11. 2nd trimester u/s
 Assessment of fetal growth
 Asymmetrical and symmetrical
IUGR
 Evaluation of polyhydramnios ,
oligohydramnous and hydrops fetals

12. 2nd trimester u/s
 Screening for abnormalities
 e.g. spina bifida, cardiac, renal
 Cervical length monitoring
 >30 mm before 18w & >25 mm
before 28 w = low risk of pre term
delivery

13.  Potential uses of ultrasound in 3rd
trimester

14. uses of ultrasound in 3rd trimester
 Assessment of fetal welbeing
 Amniotic fluid index or deepest
pool
 Fetal breathing
 Fetal movements and tone (the
Biophysical Profile)

15. uses of ultrasound in 3rd trimester
 Doppler flow studies
 In umbilical arteries
 Fetal middle cerebral artery
 Uterine arteries

16. uses of ultrasound in 3rd trimester
 Diagnosis and management of
malpresentation
 Breech and unstable or
transverse lie

17. Any Harmful Effects of ultrasound in
pregnancy:
 It is not ionising radiation
 There is no evidence that ultrasound scans are
harmful, if used according to the guidelines.
 However, theoreticaly, thermal effects and
cavitation can occur in tissues exposed to high
power ultrasound.